JP2011243746A - Semiconductor device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress semiconductor device yield reduction by forming solder bumps over electrode pads in an approximately spherical shape.SOLUTION: A semiconductor device manufacturing method includes: a step for forming a protective film 30 on a surface of a substrate 10 which has a plurality of electrode pads 60 formed on the surface; a step for forming opening portions 32 in the protective film 30 so that the plurality of electrode pads 60 are each partially exposed; a step for forming a seed film 100 over the protective film 30 and the plurality of electrode pads 60; a step for forming conductive posts 40 on the seed film 100 so as to be positioned over the plurality of electrode pads 60, respectively; a step for forming solder bumps 50 on the plurality of conductive posts 40, respectively; a step for removing parts of the seed film 100 not covered by the conductive posts 40; and a step for reflowing the solder bumps 50.

Description

  The present invention relates to a method of manufacturing a semiconductor device in which a semiconductor chip is flip-chip connected to a wiring board.

  As a mounting form that can mount a semiconductor chip having external connection terminals at a high density, there is a flip chip type semiconductor device. In a flip chip type semiconductor device, a semiconductor chip is mounted on a wiring board via bumps (external connection terminals) formed on an active surface.

  In the manufacturing process of the flip chip type semiconductor device, there is a process of reflowing solder on the semiconductor chip to form solder bumps used for flip chip connection. In the reflow process, an oxide film may be formed on the surface of the solder bump because the wafer is heat-treated at a high temperature. In this case, connection failure may occur in flip chip connection. In order to solve this problem, there is a technique described in Patent Document 1.

  The technique described in Patent Document 1 is to heat the solder paste in a nitrogen atmosphere having an oxygen concentration of 500 ppm or less in the step of reflowing the solder paste. Thus, it is described that the formation of an oxide film on the surface of the solder ball can be suppressed, and connection failure in flip chip connection can be prevented.

JP 2007-165671 A

  In a flip chip type semiconductor device, in order to provide a post, an electroplating technique using a seed film formed on one surface of a wafer as a power supply film may be used. As a result of the study by the present inventors, when the seed film is around the solder bump in the reflow process, the solder bump in a molten state may be wetted and spread. In this case, the solder bumps are not spherical, which leads to a decrease in the yield of the semiconductor device. In the technique described in Patent Document 1, the seed film is around the solder bump in the reflow process. Therefore, the technique described in Patent Document 1 cannot solve the above problem.

According to the present invention, forming a protective film on the one surface of the substrate having a plurality of electrode pads formed on one surface;
Forming an opening in the protective film such that a part of each of the plurality of electrode pads is exposed;
Forming a seed film on the protective film and the plurality of electrode pads;
Forming a conductive post on the seed film located on each of the plurality of electrodes;
Forming solder bumps on the plurality of conductive posts;
Removing a portion of the seed film not covered with the conductive post;
Reflowing the solder bump;
A method for manufacturing a semiconductor device is provided.

  According to the present invention, the reflow process is performed after the process of removing the portion of the seed film not covered with the conductive posts. Therefore, there is no seed film around the solder bump in the reflow process, and it is possible to prevent the solder bump from spreading by the seed film. Therefore, the solder bumps can be formed in a substantially spherical shape, and a decrease in the yield of the semiconductor device can be suppressed.

  According to the present invention, the solder bump formed on the electrode pad can be formed in a substantially spherical shape, and the yield reduction of the semiconductor device can be suppressed.

It is sectional drawing which shows the manufacturing method of the semiconductor device in 1st Embodiment. FIG. 3 is a cross-sectional view showing a method for manufacturing the semiconductor device shown in FIG. 1. It is sectional drawing which shows the manufacturing method of the semiconductor device in a comparative example. It is a top view which shows the semiconductor device formed with the manufacturing method of the semiconductor device shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  1 and 2 are cross-sectional views illustrating a method of manufacturing a semiconductor device according to the first embodiment. FIG. 2 shows a manufacturing process performed before the manufacturing process shown in FIG. In this manufacturing method, first, the protective film 30, the seed film 100, and the barrier metal film 110 are formed on the active surface of the substrate 10. Next, the conductive post 40 is formed. Further, solder bumps 50 are formed on the conductive posts 40. Then, the exposed portion of the seed film 100 is removed. Thereafter, the solder bumps 50 are reflowed. FIG. 4 is a plan view showing an active surface of the semiconductor device formed by the manufacturing method shown in FIG.

The semiconductor device manufacturing method according to the first embodiment will be described in detail below with reference to FIGS. As shown in FIG. 2A, a multilayer wiring layer 20 is formed on the active surface of the substrate 10 constituting the semiconductor device. The substrate 10 is made of Si, for example, and is in a state before being divided into a plurality of semiconductor chips. The multilayer wiring layer 20 is made of, for example, SiO ₂ . A protective film 22 is provided on the back surface of the substrate 10. The protective film 22 is made of, for example, Si, SiO ₂ or SiN. A plurality of electrode pads 60 are formed on the uppermost wiring layer of the multilayer wiring layer 20. The electrode pad 60 is made of, for example, Al—Si—Cu or Al.

Then, as shown in FIG. 2A, a protective film 30 is formed on the surface of the substrate 10 on which the multilayer wiring layer 20 is provided. The protective film 30 is made of, for example, SiN or SiO ₂ . Next, the protective film 30 is selectively removed. Accordingly, the opening 32 is provided in the protective film 30 so that a part of each of the plurality of electrode pads 60 is exposed. Next, as shown in FIG. 2B, the barrier metal film 110 and the seed film 100 are formed in this order on the protective film 30 and the plurality of electrode pads 60. The barrier metal film 110 is composed of a single metal such as Ti, Pd, or W, an alloy containing these, or a laminated film thereof. The seed film 100 is made of Cu, for example. The barrier metal film 110 and the seed film 100 are formed to have a thickness of about 100 to 800 nm by adding the respective film thicknesses.

  Next, as shown in FIG. 2C, a photosensitive resist 70 is formed on the seed film 100. Then, as shown in FIG. 2D, the resist 70 located on the electrode pad 60 is removed by exposure and development. As a result, an opening 72 is formed in the resist 70. Thereafter, as shown in FIG. 2E, electrolytic plating is performed using the seed film 100 as a seed. As a result, the conductive post 40 is formed in the opening 72. The conductive post 40 is made of, for example, Cu or Ni.

Then, as shown in FIG. 2F, solder bumps 50 are formed on the conductive posts 40 by electrolytic plating. As a result, bumps 80 are formed. The solder bump 50 is made of at least one of, for example, Pb, Sn, Au, Ag, Cu, In, Bi, Zn, Ni, Fe, Pd, Sb, or Ge. In the state shown in this figure, the bump 80 has a mushroom-like shape. When the resist 70 is a thick film resist, the bump 80 has a straight shape, that is, a columnar shape (not shown). Next, as shown in FIG. 1A, the resist 70 on the substrate 10 is removed. Here, after removing the resist 70, a step of removing organic substances such as a residue of the resist 70 with O ₂ plasma may be performed.

  Next, as shown in FIG. 1B, a portion of the seed film 100 that is not covered with the conductive post 40 is removed. Then, as shown in FIG. 1C, the solder bump 50 is reflowed without the seed film 100 around the solder bump 50. Thereby, the solder bump 50 becomes substantially spherical. Thereafter, as shown in FIG. 1D, a portion of the barrier metal film 110 that is not covered with the conductive post 40 is removed. As a result, as shown in FIG. 4, a semiconductor device in which a portion of the protective film 30 that is not covered with the conductive post 40 is exposed is obtained.

  Next, the effect of this embodiment will be described. FIG. 3 shows a method for manufacturing a semiconductor device in a comparative example. As shown in FIG. 3, in the comparative example, reflow is performed without removing a portion of the seed film 100 that is not covered with the conductive post 40. According to the present embodiment, reflow is performed after the step of removing the portion of the seed film 100 that is not covered with the conductive posts 40. Therefore, there is no seed film 100 around the solder bump 40 in the reflow process, so that it is possible to suppress the solder 50 from spreading by the seed film 100 as shown in FIG. Therefore, the solder 50 can be formed in a substantially spherical shape, and a decrease in the yield of the semiconductor device can be suppressed.

  Further, during the process of forming the bump 80, the protective film 30 formed on one surface of the substrate 10 is covered with the barrier metal film 110. Therefore, as compared with the case where the barrier metal film 110 is removed, it is possible to prevent defects such as cracks and peeling of the protective film 30 and bubbles generated in the bump 80 forming process including the heat treatment process and the like. Yield reduction can be suppressed. Moreover, the change of the protective film 30 can be prevented under the conditions of various reflow methods.

  Next, a second embodiment will be described. In the present embodiment, among various reflow methods that can be selected in the semiconductor device manufacturing method, a reflow method using a flux is employed. Therefore, the semiconductor device manufacturing method according to the present embodiment further includes a flux application step and a flux cleaning step in addition to the semiconductor device manufacturing method according to the first embodiment. In the present embodiment, the flux is barriered after the step of removing the portion of the seed film 100 that is not covered with the conductive posts 40 shown in FIG. 1B and before the step of reflowing the solder bumps 50. It is applied on the metal film 110 and the solder bump 50 (not shown). Further, after the step of reflowing the solder bumps 50 shown in FIG. 1C, the flux is washed (not shown).

  When the metal component constituting the solder bump 50 adheres to the surface of the barrier metal film 110, the removal of the barrier metal film 110 is hindered by the metal component in the adhered portion, or a short circuit occurs between the bumps 80 via the metal component. May happen. According to this embodiment, the flux cleaning process is performed after the reflow process and before the removal of the barrier metal film 110. For this reason, the metal component which comprises the solder 50 adhering to the barrier metal film 110 can be removed before the process of removing the barrier metal film 110. Therefore, the removal efficiency of the barrier metal film 110 can be increased and a short circuit between the bumps 80 can be prevented.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

10 substrate 20 multilayer wiring layer 22 protective film 30 protective film 32 opening 40 conductive post 50 solder bump 60 electrode pad 70 resist 72 opening 80 bump 100 seed film 110 barrier metal film

Claims (6)

Forming a protective film on the one surface of the substrate having a plurality of electrode pads formed on one surface;
Forming an opening in the protective film such that a part of each of the plurality of electrode pads is exposed;
Forming a seed film on the protective film and the plurality of electrode pads;
Forming a conductive post on the seed film located on each of the plurality of electrode pads;
Forming solder bumps on the plurality of conductive posts;
Removing a portion of the seed film not covered with the conductive post;
Reflowing the solder bump;
A method for manufacturing a semiconductor device comprising: In the manufacturing method of the semiconductor device according to claim 1,
A method of manufacturing a semiconductor device, wherein the seed film is made of Cu. In the manufacturing method of the semiconductor device according to claim 1 or 2,
Forming a barrier metal film on the protective film and the plurality of electrode pads after the step of forming the opening in the protective film and before the step of forming the seed film;
After the step of reflowing the solder bump, removing the portion of the barrier metal film that is not covered with the conductive post;
A method for manufacturing a semiconductor device further comprising: In the manufacturing method of the semiconductor device according to claim 3,
The method for manufacturing a semiconductor device, wherein the barrier metal film is composed of any one of Ti, Pd, and W. In the manufacturing method of the semiconductor device according to claim 1,
After the step of removing a portion of the seed film that is not covered with the conductive post, and before the step of reflowing the solder bump, a flux is applied on the protective film and the solder bump. And a process of
After the step of reflowing the solder bump, cleaning the flux;
A method for manufacturing a semiconductor device further comprising: In the manufacturing method of the semiconductor device according to claim 1,
The method of manufacturing a semiconductor device, wherein the solder bump is composed of at least one of Pb, Sn, Au, Ag, Cu, In, Bi, Zn, Ni, Fe, Pd, Sb, and Ge.

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